Fulminant hepatic failure (FHF) is a life-threatening disease. The definitive treatment for FHF is a liver transplant. Unfortunately, 35% of all FHF patients and 62% of nonacetaminophen-induced FHF patients die within 48 hours after reaching stage 3 or 4 coma, while awaiting a transplant. Increasing this narrow therapeutic window would provide substantially more opportunities for these patients to be transplanted. One of the primary causes of death in these individuals is cerebral edema. The mechanisms responsible for cerebral edema in these FHF patients are poorly understood. Recent evidence from other laboratories has shown that matrix metalloproteinase-9 (MMP-9) may play a pivotal role in the development of cerebral edema in other disease states. For example, treatment with either MMP-9 synthetic inhibitors or anti-MMP-9 monoclonal antibodies has been shown to result in a significant reduction in the size of cerebral infarcts. Further, studies using MMP-9 knockout mice have shown a significant attenuation in cerebral edema following either cerebral ischemic or traumatic events. Based on these data we hypothesize that MMP-9 plays a critical role in the development of cerebral edema following FHF. Significant support for this hypothesis has come from two observations made in our laboratory. First, both proMMP-9 and MMP-9 are elevated in the sera of FHF patients and in rats with experimentally induced FHF. Second, in a pilot study, we have shown that treatment with an MMP-9 inhibitor (GM6001) results in an approximate 30% reduction in cerebral edema in rats with experimentally induced FHF. In this application, we specifically propose to: 1. To further determine if inhibition of MMP-9 by the MMP synthetic inhibitor GM6001 attenuates cerebral edema in rats with experimentally induced FHF. 2. To determine whether cerebral edema is attenuated in MMP-9 knockout mice following experimentally induced FHF.